PRAGUE, April 26 (Reuters) - Czech Prime Minister Bohuslav Sobotka called on Saturday for an immediate release of a group of international observers detained by pro-Russian separatists in eastern Ukraine.

"The Czech Republic condemns the detention of international observers...calls for their immediate release," Sobotka said in a statement.

The German-led monitoring mission, made up of eight international observers including a Czech national, was detained in the city of Slaviansk on Friday. (Reporting by Jan Lopatka; Editing by Erica Billingham)